1. Field of the Invention
The present invention relates to an optical fiber holding structure. In particular, the present invention relates to an optical fiber holding structure suitable for holding optical fiber.
2. Description of the Related Art
Conventionally, an optical module component referred to as an optical receptacle has been used in optical communication using optical fiber.
FIG. 11 is a diagram of a conventionally used optical receptacle 1 such as this. The optical receptacle 1 has a roughly cylindrical holder section 2 in a right end section in FIG. 11.
A ring-shaped flange section 3 is provided around the holder section 2, near a left end section in FIG. 11.
A ring-shaped ferrule contacting section 5 is formed on an inner circumferential surface of the holder section 2 in the left end section in FIG. 11. The ferrule contacting section 5 extends in an inward radial direction (towards the center of the holder section 2). A right end surface 5a of the ferrule contacting section 5 in FIG. 11 is a contacting surface 5a that comes into contact with a ferrule, described hereafter.
A thick, disk-shaped lens section 7 is provided on the left end of the holder section 2 in FIG. 11, such as to be connected to the holder section 2. In the lens section 7, the right end surface in FIG. 11 is a flat optical surface 7a, and the left end surface in FIG. 11 is a convex surface 7b. 
A cylindrical optical device attaching section 8 is provided such as to be connected to the lens section 7. The optical device attaching section 8 extends towards a side opposite to the holder section 2. An optical device, such as a semiconductor laser, can be attached to a left end surface side of the optical device attaching section 8 in FIG. 11 by an attaching method such as adhesion.
In the optical receptacle 1 such as this, as shown in FIG. 12, a portion of optical fiber 10 that is a predetermined area on the tip side (referred to, hereinafter, as a tip end section) is inserted into the holder section 2 with a cylindrical ferrule 11 that holds the tip end section of the optical fiber 10, and is held therewithin.
In an inserted state in which the ferrule 11 is fully inserted into the holder section 2, an end surface on the optical receptacle 1 side of the ferrule 11 in FIG. 12 that is the tip end surface (left end surface in FIG. 12) comes into contact with the contacting surface 5a of the ferrule contacting section 5 of the holder section 2.
A cylindrical metal holding member 12 that holds the ferrule 11 is provided around a base end section of the ferrule 11 (end section on the side opposite to the optical receptacle 1). The holding member 12 is held within a connector casing 14 (an LC connector casing in FIG. 12).
An optical connector for connecting the optical fiber 10 to the optical receptacle 1 is configured by the ferrule 11, the holding member 12, and the connector casing 14.
In an optical connector such as this, in a state in which the tip end section of the optical fiber 10 and the ferrule 11 are inserted into the holder section 2, the tip end section of the connector casing 14 is fitted onto the outer circumferential surface of the holder section 2 such as to allow play. The connector casing 14 is then fixed to the optical receptacle 1 by a fixing means (not shown) that is a push-pull mechanism.
In this way, conventionally, the tip end section of the optical fiber 10 and the ferrule 11 are inserted into the holder section 2 of the optical receptacle 1 and held therewithin.
In a state in which the tip end section of the optical fiber 10 and the ferrule 11 are held within the holder section 2 in this way and the optical device is attached to the optical device attaching section 8, the optical receptacle 1 optically couples the optical device and the optical fiber 10 via the lens section 7.
In addition, this type of optical module in which an optical device is attached to the optical receptacle 1 has been required to have a favorable wiggle characteristic, since the past.
Here, the wiggle characteristic refers to a load characteristic of optical coupling efficiency. In a state in which the tip end section of the optical fiber and the ferrule are inserted into the optical receptacle (holder section) and the optical device is attached to the optical receptacle, when a load (referred to, hereinafter, as lateral load) is applied to the optical connector in a direction perpendicular to the optical axis of the tip end section of the optical fiber, the load characteristic of optical coupling efficiency indicates a change in coupling efficiency between the optical device and the optical fiber depending on a change in lateral load.
A favorable wiggle characteristic indicates that deterioration of coupling efficiency is small, regardless of increase in lateral load.    Patent Literature 1: Japanese Patent Laid-open Publication No. 2006-189338
However, as shown in FIG. 12, conventionally, in a state in which the tip end section of the optical fiber 10 and the ferrule 11 are inserted into the holder section 2, a gap d is formed between the holder section 2 and the holding member 12 along a longitudinal direction of the ferrule 11 (or in other words, an optical axis OA direction of the tip end section of the optical fiber 10). As a result of the gap d, the ferrule 11 and the tip end section of the optical fiber 10 are easily deformed in a direction perpendicular to the optical axis OA of the tip end section of the optical fiber 10.
Therefore, form-stability of the optical fiber 10 against lateral load cannot be maintained. As a result, a problem occurs in that the wiggle characteristic deteriorates.